The present invention relates to an integrated circuit containing bipolar and complementary MOS transistors on a common substrate wherein the emitter and base terminals of the bipolar transistors, as well as the gate electrodes of the MOS transistors, are at least partially composed of a doped silicide of a refractory metal. The invention also relates to a method for the manufacture of such integrated circuits.
An integrated circuit containing bipolar and complementary MOS transistors on a common substrate wherein the emitter terminals of the bipolar transistors as well as the gate electrodes of the MOS transistors are composed of the same material including at least one layer of a refractory metal silicide of a metal such as tantalum tungsten, molybdenum titanium or platinum is disclosed in U.S. patent application, Ser. No. 897,299, now abandoned. Utilizing such a silicide eliminates the implantation mask used in traditional methods and the contacting of base, emitter, and collector regions becomes independent of the metallization grid. U.S. Pat. No. 4,782,033 discloses a method for producing p-channel and n-channel MOS transistors comprising gate electrodes composed of a doped double layer of polysilicon and metal silicide.
In the integrated circuits disclosed in U.S. patent application, Ser. No. 897,299, now abandoned, the n-well forms the collector of the transistor and covers the n.sup.+ -doped zones that are connected in the bipolar transistor region by more deeply extending collector terminals. The advantages of the silicide or, respectively, polycide (a double layer of polysilicon and metal silicide) are thereby combined with the advantages of a deep extending collector terminal, e.g., reducing the collector series resistance and increasing the latch-up stability.
The method of the present invention provides an improvement over U.S. patent application Ser. No. 897,299 (now abandoned) in that through the method of the present invention, the base and emitter contact are formed in the same layer and, therefore, the spacing between the emitter and base contact can be further reduced and series resistances are diminished as a result thereof.